Ascending Si diffusion into growing GaN nanowires from the SiC/Si substrate: up to the solubility limit and beyond.

We report a novel mechanism that allows the incorporation of Si into GaN nanowires up to and beyond the solubility limit. This mechanism is documented during the growth on vicinal (misoriented) SiC/Si hybrid substrates having the step bunches. Nanowires that are grown at these locations become heavily Si doped. Such high Si concentrations were verified by secondary-ion mass spectrometry. Photoluminescence data also point to very high carrier concentrations. Moreover, Raman spectroscopy together with quantum chemical modelling shows the build up of Si into Ga sites and indicates even the possibility of the formation of a Ga(Si)N solid solution. The microscopic mechanism responsible for heavy doping and even alloying is diffusion driven by the mechano-chemical effect, which allows for the extremely efficient injection of Si atoms into the nanowires from the step bunches at the vicinal SiC/Si substrates.

Role of hole confinement in the recombination properties of InGaN quantum structures.

We study the isolated contribution of hole localization for well-known charge carrier recombination properties observed in conventional, polar InGaN quantum wells (QWs). This involves the interplay of charge carrier localization and non-radiative transitions, a non-exponential decay of the emission and a specific temperature dependence of the emission, denoted as "s-shape". We investigate two dimensional In0.25Ga0.75N QWs of single monolayer (ML) thickness, stacked in a superlattice with GaN barriers of 6, 12, 25 and 50 MLs. Our results are based on scanning and high-resolution transmission electron microscopy (STEM and HR-TEM), continuous-wave (CW) and time-resolved photoluminescence (TRPL) measurements as well as density functional theory (DFT) calculations. We show that the recombination processes in our structures are not affected by polarization fields and electron localization. Nevertheless, we observe all the aforementioned recombination properties typically found in standard polar InGaN quantum wells. Via decreasing the GaN barrier width to 6 MLs and below, the localization of holes in our QWs is strongly reduced. This enhances the influence of non-radiative recombination, resulting in a decreased lifetime of the emission, a weaker spectral dependence of the decay time and a reduced s-shape of the emission peak. These findings suggest that single exponential decay observed in non-polar QWs might be related to an increasing influence of non-radiative transitions.

Clinical endpoints in peripheral endovascular revascularization trials: a case for standardized definitions.

BACKGROUND: Endovascular therapy is a rapidly expanding option for the treatment of patients with peripheral arterial disease (PAD), leading to a myriad of published studies reporting on various revascularization strategies. However, these reports are often difficult to interpret and compare because they do not utilize uniform clinical endpoint definitions. Moreover, few of these studies describe clinical outcomes from a patients' perspective. METHODS AND RESULTS: The DEFINE Group is a collaborative effort of an ad-hoc multidisciplinary team from various specialties involved in peripheral arterial disease therapy in Europe and the United States. DEFINE's goal was to arrive at a broad based consensus for baseline and endpoint definitions in peripheral endovascular revascularization trials for chronic lower limb ischemia. In this project, which started in 2006, the individual team members reviewed the existing pertinent literature. Following this, a series of telephone conferences and face-to-face meetings were held to agree upon definitions. Input was also obtained from regulatory (United States Food and Drug Administration) and industry (device manufacturers with an interest in peripheral endovascular revascularization) stakeholders, respectively. The efforts resulted in the current document containing proposed baseline and endpoint definitions in chronic lower limb PAD. Although the consensus has inevitably included certain arbitrary choices and compromises, adherence to these proposed standard definitions would provide consistency across future trials, thereby facilitating evaluation of clinical effectiveness and safety of various endovascular revascularization techniques. CONCLUSION: This current document is based on a broad based consensus involving relevant stakeholders from the medical community, industry and regulatory bodies. It is proposed that the consensus document may have value for study design of future clinical trials in chronic lower limb ischemia as well as for regulatory purposes.

[Cardiopulmonary exercise testing before and after blood donation]. / Spiroergometrische Leistungsdiagnostik vor und nach Blutspende.

BACKGROUND: The link between haemoglobin and physical performance was established a long time ago and is the underlying principle of blood doping. Blood loss on the other hand decreases physical capacity. The aim of this study is to evaluate physical performance loss and underlying mechanisms following voluntary blood donation. METHOD AND PATIENTS: Eleven voluntary subjects (four female) completed a symptom-limiting cardio-pulmonary exercise test before and after blood donation (500 mL blood). RESULTS: The haemoglobin value decreased by 1.2 mg/dL (9%, p < 0.001), maximal oxygen uptake by 9% (p = 0.006), maximal work rate by 13% (p = 0.001) and duration of exercise fell from 663 down to 607 seconds (p = 0.005). Anaerobic transition occurred at 81.2% and 71.5% of maximal oxygen uptake before and after blood donation, respectively (p = 0.001). Subjects who practise recreational endurance sports appear to be more effected by endurance loss. The haemoglobin value was the only significant predictor of maximal oxygen uptake in regression analysis (p < 0.001). CONCLUSION: Maximal physical performance is impaired after blood donation. Haemoglobin decline accounts for the decreased oxygen uptake. As a consequence thereof the anaerobic transition occurs earlier. Subjects not engaged in regular sports activity did not experience a decline in their capacity. Inclusion of the haemoglobin value into equations predicting maximal oxygen uptake could improve prediction precision.

Endovascular stenting of a renal transplant vein.

We describe successful endovascular stenting of a high-grade stenosis of a renal transplant vein in a 53-year old patient. Kidney transplantation had been performed due to IgA nephropathy and the patient had become symptomatic two months after uneventful recovery from operation.

Association of cardiovascular risk factors with pattern of lower limb atherosclerosis in 2659 patients undergoing angioplasty.

OBJECTIVES: Aim of this study is to correlate distribution pattern of lower limb atherosclerosis with cardiovascular risk factor profile of patients with peripheral arterial occlusive disease (PAD). PATIENTS AND METHODS: Analysis is based on a consecutive series of 2659 patients (1583 men, 1076 women, 70+/-11 years) with chronic PAD of atherosclerotic origin undergoing primary endovascular treatment of lower extremity arteries. Pattern of atherosclerosis was grouped into iliac (n=1166), femoropopliteal (n=2151) and infrageniculate (n=888) disease defined according to target lesions treated. A multivariable multinomial logistic regression analysis was performed to assess relation with age, gender and classical cardiovascular risk factors (diabetes mellitus, arterial hypertension, hypercholesterolemia, cigarette smoking) using femoropopliteal disease as reference. RESULTS: Iliac disease was associated with younger age (RRR 0.95 per year of age, 95%-CI 0.94-0.96, p<0.001), male gender (RRR 1.32, 95%-CI 1.09-1.59, p=0.004) and cigarette smoking (RRR 2.02, 95%-CI 1.68-2.42, p<0.001). Infrageniculate disease was associated with higher age (RRR 1.02, 95%-CI 1.01-1.02, p<0.001), male gender (RRR 1.23, 95%-CI 1.06-1.41, p=0.005) and diabetes mellitus (RRR 1.68, 95%-CI 1.47-1.92, p<0.001). Hypercholesterolemia was less prevalent in patients with lesions below the knee (RRR 0.82, 95%-CI 0.71-0.94, p=0.006), whereas no distinct pattern was apparent related to arterial hypertension. CONCLUSION: Clinical phenotype of peripheral atherosclerosis varies with prevalence of cardiovascular risk factors suggesting differences in mechanisms involved in iliac as compared with infrageniculate lesions. Identification of molecular mechanism might have influence on future therapeutic strategies in PAD patients.

[Venous and lymphatic reasons for edema--the swollen leg from the angiologist's point of view]. / Phlebödem und Lymphödem--das dicke Bein aus angiologischer Sicht.

Peripheral edema develop as a consequence of imbalance in the processes of filtration, resorption and lymphatic transport in the capillary bed. Venous hypertension and impaired lymphatic function belong to the most important underlying pathomechanisms. Chronic venous insufficiency as a result of valve degeneration as well as venous obstruction in acute deep thrombosis lead to venous hypertension and to an increase of filtration pressure. As venous diseases are frequent, they are one of the most reasons for a swollen leg in clinical everyday life. Primary and secondary disturbances of the lymphatic system are another important reason for interstitial liquid retention. Although there are about 140 millions of people suffering from lymphedema worldwide, the disease is still underdiagnosed.

Delay of dialysis in end-stage renal failure: prospective study on percutaneous renal artery interventions.

BACKGROUND: Renal artery stenosis (RAS) is a cause of end-stage renal failure. We studied the effect of percutaneous renal artery intervention (PRI) in patients with advanced, progressive disease at risk for renal failure, hypothesizing a beneficial effect. METHODS: Thirty-nine primary and 14 secondary PRIs were performed on 28 patients with atherosclerotic RAS, serum creatinine >300 micromol/L, and progressive loss of renal function >/=1 year before PRI. Renal function and RA patency were prospectively followed for 12 months after primary and secondary PRI. The intervention's effect on the progressive loss of renal function was calculated by comparing reciprocal slopes of serum creatinine against time before and after PRI. RESULTS: Progression of renal failure slowed significantly following PRI. Mean (+/-SE) slopes of reciprocal serum creatinine values were: 6.69 +/- 0.97 L micromol(-1) day(-1) (x10(-6)) before and 6.76 +/- 3.03 L micromol(-1) day(-1) (x10(-6)) after PRI (P= 0.0007). Fifteen patients (53.5%) showed improvement or stabilization of progressive renal dysfunction. Out of 11 patients expected to become dialysis dependent within one year, 8 (72.7%) experienced an improvement in renal function sufficient to remain dialysis-free. Favorable outcome correlated with a lower creatinine level (P= 0.0137) and a more negative slope of progression (r= 0.49, P= 0.020) at entry. Mortality was 10.7%, and rate of local complications was 7.1%. Deterioration of renal function following PRI was suspected in 17.9% of patients. CONCLUSION: PRI may improve renal function and ultimately delay dialysis in patients with advanced renal failure. Possible advantages must be weighed against the risk of renal failure advancement and high procedure-related complication rate.

Double-blind, randomized, controlled study on the efficacy and safety of a novel diclofenac epolamine gel formulated with lecithin for the treatment of sprains, strains and contusions.

To evaluate the efficacy of the new diclofenac-N-(2-hydroxyethyl)-pyrrolidine gel formulated with lecithin (DHEP lecithin) compared with diclofenac-N-(2-hydroxyethyl)-pyrrolidine gel (DHEP gel) without lecithin in mild-to-moderate posttraumatic injuries (grade 1 ankle, knee and muscle injuries), a multicenter, double-blind, controlled study was carried out. A total of 100 patients were enrolled and randomly assigned to either DHEP lecithin (n = 52) or DHEP gel (n = 48) treatment. All patients concluded the treatment period except for five, who did not turn up to their respective investigational sites for the follow-up visits. According to an intention-to-treat approach, they were all included in the statistical analysis. As for the efficacy and safety analysis, the primary variable was "pain on movement" as measured by a Huskisson visual analog scale. During the first 3 days of treatment each group recorded a significant within-group decrease, but patients treated with DHEP lecithin showed a decrease in absolute value that was statistically greater than that obtained with DHEP gel (p = 0.025). At the end of the treatment period (day 10) the difference between groups was still statistically significant (p = 0.036). The statistical analysis of the secondary efficacy variables showed significant results in favor of DHEP lecithin treatment. These were superimposable on the results found for the primary variable. The global efficacy and tolerability judgments, reported either by patient or by physician, showed no statistical difference between treatment groups. Due to the presence of lecithin in the new gel formulation, DHEP lecithin showed a faster and significantly more marked therapeutic effect compared with that of DHEP gel.

Does infection affect amputation rate in chronic critical leg ischemia?

BACKGROUND: Aim was to analyze the association between local infection and amputation rate in patients with chronic critical limb ischemia (CLI) with or without successful revascularization. PATIENTS AND METHODS: We performed a retrospective analysis of 56 consecutive patients with 57 critically ischemic legs seen at the University Hospital Bern. Patients with CLI were selected if ischemic lesions and follow-up of more than 2 months were documented. Infection was suggested when 2 of the following criterion were present: temperature > 37 degrees C, C-reactive protein > 50 mg/L, leukocytes > 10 x 10(3)/microliter ("2 of 3" criterion), or a putrid secretion was documented ("secretion" criterion). RESULTS: In patients with successful revascularization (n = 39), there was a significant shift from 10.3% major to 33.3% minor amputations (Chi Square p value = 0.014) as compared to patients without or with failed revascularization (n = 18) with 44.4% and 11.1% (Chi Square p value = 0.008), respectively. An infection was suggested in 22 of 53 limbs (41.5%) according to the "2 of 3" criterion, and 30 of 57 limbs (52.6%) satisfying the "secretion" criterion. Both criteria, were significantly more common in patients undergoing amputation as compared to patients without amputation (p = 0.001). Multiple lesions were more common in patients with major amputations (p = 0.026). CONCLUSION: Successful revascularization effectively reduces major amputations and leads to healing of ischemic ulcers. Secondary foot infections are frequent. Infections are associated with a significantly higher rate of minor and major amputations, also in patients with successful revascularization, and should be treated adequately as well as in time with antibiotics.

[Anticoagulation and antiaggregation in patients with peripheral arterial occlusive diseases]. / Antikoagulation und Antiaggregation beim Patienten mit PAVK.

Peripheral vascular occlusive disease (PAOD) is frequently seen in patients suffering from coronary heart or cerebrovascular disease and is, considered as a prognostic predictor for the morbidity and mortality of this patient group. Thus, secondary antithrombotic and antiplatelet prophylaxis in these patients is not limited to achievement of long-term patency of the revascularized or recanalized arterial segment, but plays as well a pivotal role for the prevention of myocardial infarction and stroke. Generally, claudicants as well as patients undergoing percutaneous transluminal angioplasty (PTA), supragenicular femoro-popliteal artificial bypass surgery, aortofemoral, iliaco-femoral unilateral bypass, or aortobifemoral Y-graft implantation with unimpaired arterial outflow are treated life-long with low dose acetylsalicylic acid (ASA) 75-250 mg. On the other hand, those undergoing axillo-femoral, femoro-femoral crossover, aorto-profundal or femoro-popliteal infragenicular and femoro-distal venous bypass surgery should be treated with vitamin K antagonists. The role of Clopidogrel in secondary prevention after peripheral revascularization and recanalization still needs to be defined.

Evaluation of clinical tests to assess perfusion in chronic critical limb ischemia.

BACKGROUND: Evaluation of macro- and microcirculatory tests to confirm diagnosis, and recognize perfusion changes in chronic critical limb ischemia (CLI). PATIENTS AND METHODS: Forty-two consecutive patients with CLI examined at the University Hospital Bern, with 21 included in this prospective follow-up analysis. Patients underwent serial clinical examinations, and assessment of the macro- (ankle arterial pressure [AP], great toe pressure [TP], oscillography) and microcirculation (transcutaneous partial oxygen pressure [tcPO2] recumbent, sitting, O2-inhalation; capillary microscopy) at baseline, 6 weeks after revascularization (group 1; [n = 11]), or after 10 weeks in patients unsuitable for revascularization (group 2; [n = 10]). Clinical improvement was considered to indicate increased perfusion. RESULTS: Eleven patients with revascularization (11/11), and 2 without revascularization (2/10) showed clinical improvement. AP measurements were not reliable or feasible in 9 (43%), TP in 4 patients (19%), respectively. All measurable pressures were in accordance to clinical course. Oszillography gave a moderate perception of perfusion changes. Baseline tcPO2 levels were critical (< 30 mmHg) in all 21 patients, whereas follow-up gave poor correlation with the clinical course. Reliability to detect perfusion changes increased by adding provocation manoeuvers in patients with clinical improvement (39% [5/13] recumbent, 77% [10/13] sitting, 85% [11/13] O2-inhalation). Capillary microscopy revealed a relevant pathology at the forefoot level in all patients with feasible examinations (18/21), and significant improvements according to the clinical course in 92% of patients (12/13). CONCLUSIONS: TP measurements represented most reliable test to confirm diagnosis and disclose improved perfusion in CLI. TcPO2 measurements in recumbent position gave unreliable results, improved by provocation manoeuvers. Capillary microscopy was reliable, but time consuming and limited by anatomical restrictions.

Effects of exercise training program on functional capacity and quality of life in patients with peripheral arterial occlusive disease. Evaluation of a pilot project.

BACKGROUND: In patients with peripheral arterial occlusive disease (PAOD) stage II, exercise training seems to be important to reduce symptoms and improve functional capacity. We evaluated the effects of an out-patient treatment program on walking distance (standardized treadmill testing), training exercise capacity, and disease specific quality of life (PAVK-86 questionnaire). METHODS AND RESULTS: Thirty-one patients aged 70 +/- 2 with intermittent claudicatio in stage IIa/IIb according to Fontaine (n = 18/13) underwent a supervised 12 week exercise training and education outpatient program. During course of intervention, patients demonstrated improvements in pain-free training walking distance (p < 0.001) and repetitions of tiptoe standing (p < 0.05). In standardized treadmill testing, pain-free walking distance was improved by 182% (129 +/- 19 m-->364 +/- 53 m; p < 0.001), and maximum walking distance by 76% (311 +/- 42 m-->546 +/- 63 m; p < 0.01). Before training, mean subscale scores of the PAVK-86 demonstrated distinct impairments concerning pain and functional status. After 12 weeks of intervention, with exception of the subscale complaints, all dimensions of quality of life assessed have improved significantly. The highest effect size was observed for the subscales pain, mood, and functional status. Improvement in the subscale anxiety and pain-free walking distance (treadmill test) correlated significantly (r = 0.46) as well as improvement in the subscale mood and maximum walking distance (r = 0.45). CONCLUSION: In patients with PAOD stage II considerable effects on functional capacity and important dimensions of quality of life can be achieved by a short exercise and education program.

Treatment of renal artery fibromuscular dysplasia with balloon angioplasty: a prospective follow-up study.

OBJECTIVES: to assess restenosis rates and blood pressure response after percutaneous transluminal renal angioplasty (PTRA) in patients treated for fibromuscular dysplastic renal artery stenosis. METHODS: a prospective 12-month follow-up study of 27 patients with 31 treated renal artery stenosis. Follow-up assessment included colour-coded duplex sonography (CCD) of renal arteries, monitoring of blood pressure, antihypertensive medication, and creatinine measurements before discharge and at 3, 6, and 12 months. Primary end point was defined as a haemodynamically significant restenosis >60% assessed by CCD. RESULTS: there was a cumulative 23% restenosis rate at 12 months. Arterial hypertension was cured or improved in 93% of patients immediately after the intervention and remained cured/improved in 74% of patients at 12 months of follow-up. Renal failure present in five patients before PTRA stabilised or improved in all patients. CONCLUSION: although restenosis rate after PTRA in fibromuscular dysplasia is as high as in non-ostial atherosclerotic lesions, there remains a considerable higher therapeutic effect. Profound pressure response and recurrent arterial hypertension with restenosis support the high probability of a renovascular origin of arterial hypertension in this young and otherwise healthy population compared to patients with atherosclerotic renal artery lesions.

[Treatment of peripheral arterial occlusive disease]. / Behandlung der peripher arteriellen Verschlusskrankheit.

The choice of therapy for peripheral artery occlusive disease depends on functional stage, site and extent of vascular lesion, pathogenesis, and the individual needs of the patients. In stage I (according to Fontaine) the risk factors are sought and treated. In stage II walking exercise is the main pillar besides vasoactive drugs and secondary drug prevention. Transluminal angioplasty is recommended if vascular lesions are suitable (short stenoses or occlusions in iliac a/o femoro-popliteal arteries). Surgery may be performed in aorto-iliac arteries but only exceptionally in femoro-popliteal disease. In stage III/IV or chronic critical ischemia every possibility for revascularisation must be considered. In acute stages immediate therapy is necessary. In our hands catheter techniques (thrombolysis a/o aspiration) are the first line approach on the femoro-popliteal level while occlusions on aorto-iliac level are left to surgery.